DALLAS (AP) _ A 1-year-old girl was in serious condition today after her 2-year-old brother shot her in the head with a handgun he found in his mother's purse, hospital officials said.

The shooting occurred about 1:15 p.m. Thursday as the girl, Ashley Leann Romans; her brother, Wesley Romans; and their 4-year-old brother, Richie Romans, were playing in the bedroom of their mother's apartment, police said.

The mother, Sherry Rodriquez, 21, and the children's grandmother were in another part of the apartment at the time.

Police Sgt. G.S. Beck said the boys told police the 2-year-old found a .45- caliber handgun in their mother's purse and was playing with it when the gun went off. The bullet struck the girl in the back of the head and exited near her right temple, Beck said.

''He was crying,'' he said of Wesley. ''He knew he shot his little sister.''