Grief-stricken mother kills herself and two daughters with nitrogen gas, three months after her soldier son's suicide

A mother depressed over her son's suicide killed her two young daughters and herself early Tuesday using suffocating nitrogen gas at their upstate New York home, about a week after a stay in a mental institution, authorities said.

East Greenbush Police Chief Christopher Lavin said a 911 call at about 1.45am sent police to the town house in the Albany suburb, where they found the mom and girls, ages 6 and 9, unconscious from exposure to the odorless gas in a first-floor bedroom.

Rescuers had to break down the door to the locked room and tried CPR for a half hour before the three were taken to Albany Medical Center, where they died.

The mother, 47-year-old Angela Mtambu, was recently released from a Pennsylvania mental institution after being overcome with grief when her 23-year-old son, Mitchell Gwatida, asphyxiated himself in the same home in April, authorities said.

'I just think she couldn't take it,' the woman's brother, Bernard Pamberi, told reporters outside the home as he fought back tears.

Horrific scene: Bernard Pamberi holds back tears as he speaks of breaking into his sister's bedroom and finding her and his two nieces with plastic bags over their heads next two two tanks of gas

Police said the father of the girls, Callidora and Eudora Thurston, has been notified.

Angela Mtambu was a traveling nurse who was working in Houston this spring when she decided to return to the home she has owned for 12 years.

A Texas relative who was concerned that the distraught Mtambu might be planning to kill herself and her daughters notified authorities in East Greenbush, and an Amber Alert was issued June 1.

Mtambu was taken into protective custody in Harrisburg, Pennsylvania, and local social services took custody of the two girls, Lavin said.

Mtambu was kept nearly three weeks for psychiatric observation before being allowed to reunite with her daughters and no order of protection was issued.

'She apparently did not exhibit behavior that is needed to trigger a preventative-custody arrest,' Lavin said.'I can't think of anything under the law that we could have done.'

Lavin said she rejoined her family last week, social services followed up with visits to check on the children's welfare, and on Sunday night she was again allowed to sleep in the same room with her daughters.

'There was no sign. We spent the whole day, yesterday, with the children,' Pamberi said. 'We went for dinner at Applebee's restaurant. We took them for ice cream.'

Pamberi and the other uncle who were staying in the home said they awakened to the sound of hissing gas Tuesday morning but couldn't get out of their room because they had been locked in. Pamberi said he then made the emergency call.

Lavin said three police officers were the first to arrive at the scene and were affected by the high level of nitrogen gas. They weren't injured. He said more than one 30-pound tank of the gas was found in the room.

According to Pamberi, his sister and nieces were wearing plastic bags over their heads.

Lavin said it is possible Mtambu intended to mimic the death of her son, who took his own life in the very same room at 58 Rockrose Drive as his mother.