Hundreds of people gathered at a suburban St. Louis gas station early Wednesday morning after a police officer shot and killed an 18-year-old man who had been pointing a 9 mm handgun at the officer, authorities said.

Some protesters among the angry crowd of between 200 and 300 turned violent early Wednesday morning, setting off explosive devices and throwing bricks and rocks, St. Louis County Police Chief Jon Belmar said at a press conference.(talk about your regular Gotham police department.).

More than 50 police officers, some in riot gear, responded, and video showed officers wrestling with protesters.

Four suspects were arrested on charges of assaulting police officers at the Mobil gas station on Hanley Road in Berkeley, just miles from the site of 18-year-old Michael Brown’s death in Ferguson last August.

“To come there armed with explosive devices is certainly something that is not safe for our community, not safe for our businesses, certainly not safe for our police officers,” Belmar said.

At least two officers were taken to emergency rooms: one for lower leg injuries from one of the blasts, another for facial abrasions from a brick, according to police.

Arsonists set fire to a QuikTrip convenience store across the street, but the fire was extinguished, Belmar said.

“We did not deploy tear gas. We did not deploy flashbangs. No officers down there did that,” Belmar said.

Belmar said he spoke to several young people at the scene who questioned why the officer did not use a Taser or Mace pepper spray to incapacitate the suspect, rather than a firearm.

“Frankly, that’s unreasonable,” he said. “When we have someone that’s pointing a gun at a police officer, there’s not a lot of time. I would imagine that most of us would feel like we were in imminent danger of losing our lives at that point.”

Belmar says he empathizes with the young men but believes the officer responded with “commensurate force.”

“I understand that these young people are looking for something, but I think these young people need to understand the context of what happens down there with these kinds of situations,” he said.

The department identified the 18-year-old man who died as Antonio Martin of St. Louis. Toni Martin, a woman at the chaotic scene, told the St. Louis Post-Dispatch that it was her son.

Belmar said the 18-year-old already had a criminal history, including armed robbery and assault charges.

The department, he said, will continue to investigate the case and present the evidence to the prosecutor's office.

Missouri Gov. Jay Nixon commended Berkeley police.

"The events in Berkeley are a reminder that law enforcement officers have a difficult, and often dangerous, job in protecting themselves and law-abiding citizens," Nixon said in a statement.