Story highlights Police say a man with a rifle fired into a back room of the barbershop

20 to 30 men were gambling in the room, they say

Police are questioning a "person of interest"

Three men were killed and nine wounded in Detroit on Wednesday when a man fired a high-powered rifle into the back room of a barbershop where 20 to 30 men were gambling, police said Thursday.

Authorities were questioning a "person of interest" taken into custody while wearing body armor. The man, a convicted felon, has not been charged in the slayings, Detroit Police Chief James Craig said at a news conference.

The shooting apparently stemmed from "an ongoing feud between a particular individual and members of the gambling party," Craig said.

Word of the killings first spread on Twitter.

Craig said a man inside an automobile fired at another vehicle outside the business on the east side of Detroit. The shooter got out of his car and fired the rifle into the back room of the barbershop, where men had gathered to gamble, he said.

At least one man in the room had a weapon and fired back. The men tried to flee to the front of the barbershop, but the door opened inward, slowing their escape, Craig said.

Detroit long has endured gun violence, but the barbershop shooting "certainly rises up as one of Detroit's more violent incidents," Craig said.

Nevertheless, overall violent crime is down about 6%, he said.