SAN FRANCISCO (AP) — Police say they are looking for a group of "cowards" who beat a homeless man to death as he slept in an alley in downtown San Francisco.

Police spokesman Albie Esparza said Wednesday that Tai Lam's body was found inside a sleeping bag.

Esparza tells KGO-TV (http://abc7ne.ws/1pp3Z8Y ) that the 67-year-old man was "savagely" beaten by three suspects early Monday. Investigators are reviewing surveillance footage in an effort to locate them.

Esparza says Tai was not robbed, and there was no clear motive in the attack. He says it was "a vicious, unprovoked attack by these coward suspects."

Esparza says investigators hope to release a description of the suspects soon.