#IfTheyGunedMeDown
The #IfTheyGunedMeDown hashtag went viral on Twitter in the wake of Michael Brown's shootingTwitter/@MrFantastic-Lo

Hundreds of protestors gathered outside a St. Louis police station, demanding murder charges against an officer who shot to death Michael Brown.

Around 15 people were arrested during the mostly peaceful protests after a night of rioting. About 12 business were damaged in the rioting, with 32 people arrested and two officers injuring according to a Reuters report.

"It breaks my heart," Ferguson Police Chief Tom Jackson told journalists on Monday. "Last night was the worst night of my life."

The FBI is looking into civil rights violations in the case, said a spokeswoman for the agency, while St. Louis County police is leading the investigation into the shooting.

The dead teenager's family requested for calm and an end to the street violence, according to media reports. Lawyer Benjamin Crump has been hired by the family. He represented the family of Trayvon Martin, a black Florida teenager who was unarmed when he was shot and killed by George Zimmerman, a neighborhood watchman in 2012.

Protesters at Monday's gathering shouted "Stop the killer cops" and "No justice, no peace."

Brown was shot on Saturday afternoon after a struggle over a gun in a police car. It was not immediately clear why Brown was in the car. At least one shot was fired during the struggle, and the officer reportedly fired more shots before leaving the car.

The officer, who has not yet been identified, is a six-year veteran and has been put on administrative leave. The officer's race has not been disclosed.

Three of the Ferguson Police Department's 53 members are black, said Police Chief Jackson.

About two-thirds of Ferguson's population of about 21,000 are black, according to U.S. Census figures.

"There's a long history of racial injustice," said Terry Jones, political science professor at University of Missouri-St. Louis. "Slowly and not so surely, the St. Louis metropolitan area has been trying to figure out a way forward. As the Michael Brown shooting indicates, there are often setbacks."

More than 300 police officers, many in riot gear, tried to control the crowd on Sunday night, said St. Louis County Police spokesman Brian Schellman. Sunday's protests turned violent after dark, with rioters smashing windows of stores and restaurants and damaging cars.

On a vacant building next door, someone had used red-orange paint to write: "The only good cop is a dead cop."