A Texas woman unable to qualify for food stamps for months walked into a state welfare office with a gun, then shot her two children and killed herself during a seven-hour standoff, officials said Tuesday.

The children, a 10-year-old boy and a 12-year-old girl, were in critical condition Tuesday, said police investigator Joe Baeza in Laredo, Texas.

The standoff began around 5 p.m. Monday afternoon. Baeza said the woman was speaking with two employees when she pulled out a gun and said she wanted to speak to a supervisor. When the supervisor arrived, he convinced her to let the employees go in exchange for keeping him.

Meanwhile, about 25 other people were moved to safety, police said.

The identity of the mother and children were still not made public as of early Tuesday afternoon.

Texas Health and Human Services spokeswoman Stephanie Goodman said Tuesday the woman first applied for assistance in July. Goodman said the mother was denied because she didn't submit enough information.

Goodman said the mother called the office in mid-November to check on her case. That was apparently the last time she tried contacting the state before Monday's shooting, Goodman said.

Goodman said the woman specifically requested to speak with a different caseworker, other than the one she had been working with, when she entered the building Monday. She was escorted to a private room and revealed a gun shortly after, Goodman said.

Police negotiators stayed on the phone with the woman throughout the evening, but she kept hanging up. She let the supervisor go unharmed around 7:45, but stayed inside the office with her children. After hanging up the phone around 11:45, police heard three shots, and a SWAT team entered the building. Inside, they found her body and her two wounded children.

The 38-year-old woman had recently moved to the area from Ohio, Baeza said.

She told negotiators about a litany of complaints against state and federal government agencies, though it wasn't clear what specifically triggered Monday's standoff.

"This wasn't like a knee-jerk reaction," Baeza said, adding that the woman felt she was owed restitution of some sort.

A spokeswoman for the state's welfare agency did not immediately return a call Tuesday seeking comment.