LOWELL, Mass. (AP) _ A man went to his girlfriend's apartment and shot her four children, stabbing one boy with a machete as well, authorities said. All four were in critical condition.

Vuthy Seng, 34, was arrested at a friend's house about three hours after the Sunday evening attack on the three boys and a girl, ranging in age from 9 to 15.

Police spokesman Kurt Sanborn said the attack was being treated as a case of domestic violence but the precise motive was unknown. It was unclear whether the mother was home when her children were shot, he said.

``He went there specifically to hurt the children,'' Lowell Police Detective Lt. William Taylor said.

Rescue workers, alerted by several 911 calls, found two of the children in a back bedroom and two in the kitchen.

The children, covered with blood and fitted with neck braces, were carried out on stretchers one by one into the building's dimly lit parking lot, as stunned neighbors watched.

``This has always been a quiet neighborhood,'' said one, Charles Racette.

Seng, described as a slight man, just over 5 feet tall and about 100 pounds, was not armed and went quietly with police. One of the victims provided information that led police to the suspect, Sanborn said.

Seng, who police said worked at a plastics factory, faced four counts of assault with intent to murder.

The children were transferred by helicopter from Lowell hospitals to Boston-area hospitals, where they were in critical condition today. The 15-year-old boy was stabbed as well as shot.