Prominent Ugandan gay rights activist, David Kato, whose picture was published by an anti-gay newspaper next to the words "Hang Them" was bludgeoned to death. Police said Thursday his sexual orientation had nothing to do with the killing and that one "robber" had been arrested.

Activists were outraged over the death of David Kato, an advocacy officer for the gay rights group Sexual Minorities Uganda. His slaying comes after a year of stepped up threats against gays in Uganda, where a controversial bill has proposed the death penalty for some homosexual acts.

Kato, who had received multiple threats, was found with serious wounds to his head caused by an attack with a hammer at his home late Wednesday in Uganda's capital, Kampala. Kato later died on the way to the hospital.

"We are horrified and saddened by the murder of prominent human rights activist David Kato in Uganda yesterday afternoon," Assistant Secretary of State for African Affairs Johnnie Carson posted on Twitter.

Human Rights Watch called for an urgent investigation, saying that Kato's work as a prominent gay rights campaigner had previously seen him face threats to his personal safety.