Terrel Harris of the state Executive Office of Public Safety and Security says the medical examiner hasn’t determined the cause of death of 26-year-old Tamerlan Tsarnaev.

Tsarnaev and his brother, 19-year-old Dzhokhar, are accused of planting two explosives near the marathon finish line

Monday, killing three people and injuring more than 180. A motive remains unclear.

The older brother was killed during a getaway attempt early Friday. Police say he was run over by a car driven by his brother as he fled the gunfire. The younger brother was captured Friday night after a gunbattle with police and remains hospitalized in serious condition.

(Photo courtesy of Associated Press)

Arriving police spotted two injured men on the ground in a parking lot and one of them reached for a gun as the officers moved in to assist them.

Schrock says officers then opened fire. The man was killed but it wasn’t immediately clear if it was from police gunfire.

The other man one the ground and another man in the parking lot were found dead.

In a search of the complex, police found yet another man dead in one apartment and a slain woman in another.

There was no immediate word what set off the gunfire.

(Photo courtesy of the Associated Press)

Texas Department of Public Safety Sgt. Jason Reyes said Friday that about 200 people were injured in the explosion at facility Wednesday night in the small farming community of West, about 20 miles north of Waco.

Search and rescue crews have been sifting through the still-smoldering remains for survivors. That work continues. The blast crumpled dozens of homes, an apartment building, a school and a nursing home.

Authorities say there’s no indication that the blast was anything other than an industrial accident sparked by a fire. The company has been cited for apparently minor safety and permitting violations over the past decade.

(Related: Local responders discuss disaster preparedness)

The sound of gunfire has been reported in Watertown, Mass., where authorities have been searching for a suspect in the Boston Marathon bombings.

The AP reports emergency and military vehicles are speeding through town. Police say multiple shots have been fired. Boston Police say people should stay inside around a street in Watertown.

It wasn’t immediately clear whether authorities had found 19-year-old college student Dzhokhar Tsarnaev. Authorities are telling residents of the area to stay indoors.

***Update at 8:55 a.m.***

The Massachusetts Institute of Technology police officer said to have been shot and killed by the Boston Marathon bombing suspects has been identified as 26-year-old Sean Collier.

The Middlesex district attorney’s office says Collier was a Somerville resident who had worked at MIT since January 2012. Before that, he was a civilian employee of the Somerville Police Department.

MIT Police Chief John DiFava says Collier was a dedicated officer who was liked by his colleagues and the MIT community.

Collier was found shot several times in his vehicle in Cambridge at about 10:30 p.m. Thursday. He was pronounced dead at Massachusetts General Hospital.

Authorities say he was shot by the two suspects in Monday’s marathon bombings.

***Update at 7:50 a.m.***

Police commissioner says Boston residents are urged to stay in homes as the hunt for the 19-year-old Tsarnaev (pictured) goes on. Three law enforcement sources, and the uncle of Boston Marathon bomb suspects confirm the men were brothers.

***Update at 5:55 a.m.***

Surviving Boston bomb suspect identified as Dzhokhar A. Tsarnaev, 19, of Cambridge, Mass. AP sources say Boston bomb suspects from Russia region near Chechnya, and lived in the U.S. at least 1 year.

***Update at 5:00 a.m.***

WATERTOWN, Mass. (AP) – Authorities say one of two suspects in the Boston Marathon bombing is dead and a massive manhunt is underway for another.

Residents of the Boston suburb of Watertown have been advised to keep their doors locked and not let anyone in.

The Middlesex district attorney says the two men are suspected of killing an MIT police officer at the college late Thursday, then stealing a car at gunpoint and later releasing its driver unharmed. Hours earlier, police had released photos of the bombing suspects and asked for the public’s help finding them.

Authorities say the suspects threw explosives from the car as police followed it into Watertown. The suspects and police exchanged gunfire and one of the suspects was critically injured and later died.

Police say the suspect on the loose is a “terrorist” who “came here to kill people.”

Three people died in the Boston Marathon bombings Monday. More than 200 runners from Missouri, 16 out of Columbia alone, competed in the race, but we’ve heard no reports that any of them are hurt.

The agency released multiple photos of a man in a white hat and one in a black hat at a press conference Thursday.

Lead investigator Richard Deslauriers says the FBI considers the two men armed and extremely dangerous. He says investigators think the men worked together, dropping bags in the same areas where two homemade bombs exploded on Monday.

The FBI said he was suspected of mailing letters to President Barack Obama and Mississippi Sen. Roger Wicker that were intercepted Tuesday and tested positive for the poison. Conclusive tests were pending.

Police in Corinth had Curtis’ home in a subdivision surrounded by yellow crime scene tape, though neighbors weren’t evacuated. It wasn’t clear where he was being held.

Officials say more than 100 people have been injured.

The explosion has also leveled buildings for blocks in every direction. Al Vanek, a city council member, says a four-block area around the explosion “is totally decimated.”

Some of damaged buildings are a housing complex with a collapsed roof, a nearby middle school and the West Rest Haven Nursing Home, where first-responders evacuated more than 130 patients.

Residents who have not evacuated are being told to stay indoors because of the threat of new explosions or leaks of ammonia from the plant.

West Mayor Tommy Muska says there were five or six volunteer firefighters battling the blaze at the West Fertilizer plant when the explosion happened just before 8 p.m. Wednesday.

Muska, who is a volunteer firefighter himself, says not all of his fellow firefighters are accounted for. He says the blast knocked his helmet off and shattered the windows of his nearby home.

Authorities say an unknown number of people were killed in the blast, which leveled buildings for blocks in every direction.

The zoo lets the giraffes out when it’s 45 degrees and sunny or 50 degrees and raining. Though their species is native to Africa, they can withstand those temperatures because they were born in in the U.S.

But unlike Dave, the adult giraffes were much more subdued than usual. Amy Roberts, the zoo’s curator of mammals, says they, like many humans, may be waiting for warmer temperatures to really let loose.

The president’s approach underscores the struggle to piece together information about what happened Monday at the finish line of the famous race, as well the White House’s lessons learned from previous terrorist incidents. That includes last year’s deadly attack on a U.S. diplomatic compound in Benghazi, Libya, which the Obama administration was reluctant to call terrorism.