A man wielding a chain saw and a knife attacked residents at a homeless shelter where he was staying, leaving two people in critical condition and injuring two others, police said.

Matthew Watkins, 28, was charged with four counts each of first-degree assault and armed criminal action for the attack Saturday at the Mid-America Care Center, the Callaway County sheriff's office said Sunday.

Sheriff Dennis Crane said two victims were cut by a chain saw and two others by a knife. Authorities said the victims injured by the chain saw were in critical condition, while the other two were treated and released.

Watkins had been staying at the shelter for about two weeks and was taking part in a program that provides residents with on-the-job-training, authorities said.

The attacks happened around 2 p.m. inside the shelter. Afterward, Watkins ran outside, where police got him to drop the chain saw at gunpoint and arrested him, authorities said.

Watkins, originally from St. Louis, was being held on $600,000 bond. Jail officials did not immediately know whether Watkins had an attorney.