A stabbing attack at a homeless shelter sent 11 people to a hospital Sunday night in Salem, Oregon, and a man was in custody, a police spokesperson said.

Police were called out at about 7:15 p.m. Sunday to the Union Gospel Mission, Angela Hedrick of the Salem Police Department said in a statement. She said the victims suffered "varying types of injuries" and that their status was unknown.

Executive Director Craig Smith told NBC News late Sunday that the attacker was new to the mission, having spent Saturday night there, and was about to check in for a second night when he got into a fight.

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"Something ... set him off, and he evidently had a knife in his bag," Smith said.

The altercation happened right before the man would have handed over his belongings to staff, and at least one staffer, who was working the mission's check-in desk, was injured in the attack, Smith said.

Bobby Epperly was on the second floor when he said he saw the man screaming outside at traffic and holding a knife, the Salem Statesman Journal reported.

"It's like a horror movie," said Epperly, 48. He said he didn't realize some people had already been stabbed inside the building until he went downstairs and saw "blood everywhere."

Hedrick released no more details as detectives investigate. Messages seeking comment were left with the hospital and at the mission, where up to 150 homeless men seek refuge each night, according to its website.