A woman in her late 50s was attacked and beaten with a hammer and the suspect is her grandson, San Antonio police say.

That attack happened just after 10 p.m. Saturday at a home in the 900 block of Rigsby Avenue.

Officers found the grandmother on the ground and badly bleeding. EMS transported the woman to SAMMC with critical head injuries.

Police say they arrested the suspect at a different location and he admitted to attacking a woman with a hammer, then said he was her grandson. 

Police are investigating what provoked the attack and have not announced any charges. The suspect's name has not been released.