A pregnant woman and her friend were stabbed on a subway on Thursday night, police say. And sources tells DNAinfo that the pregnant woman's leg "leg bumped Derrick Wilson, 50, and sent him into a rage about 6:41 p.m."

The 24-year-old pregnant woman and her female friend, 21, were on a northbound 2 train in the Bronx. According to DNAinfo, a source said the pregnant woman "was sitting on the lap of her friend" when she apparently bumped into Wilson. That when Wilson allegedly took out a knife, stabbing the four-months pregnant woman in the neck and her friend in the left bicep.

Wilson fled at the elevated Prospect Avenue station, reportedly throwing the knife onto a rooftop; the Daily News adds, "A group of good Samaritans chased after him and held him until police arrived."

One of the Good Samaritans told WCBS 2, "I heard some commotion that somebody got stabbed. “Me and a couple of other guys, we said ‘where’s he at.’ We came looking for him and he ran out. He came past me and I grabbed him."

"One witness said the crowd wanted to rough up Wilson, but he eventually talked them out of it," per NBC New York.

The victims were taken to Lincoln Hospital in critical but stable condition.

Wilson was charged with attempted murder, assault and menacing.