CUMBERLAND COUNTY, N.J. -- A New Jersey man shot and killed his estranged wife in front of their two children on Sunday, and then critically injured himself when he tried to commit suicide after the shooting, police said.

The victim, Sharon Bortle, 35, was an elementary school teacher.

Frank Bortle, 45, shot his wife during an apparent custody argument while she was sitting in her SUV with their 4-year-old daughter Sunday afternoon outside his home along West Wheat Road in Vineland, Cumberland County, according to police.

Frank Bortle remained in critical but stable condition and under police guard at Cooper Hospital Monday.

The mother was at Frank Bortle's home to pick up their son.

Investigators said the 9-year-old boy witnessed the shooting and ran next door to his grandfather's house to call 911.

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The two children were not physically hurt and are now staying with their maternal grandparents.

Fourth-graders at Marie D. Durand Elementary in Vineland were figuring out how to come to terms with the way their teacher died over the weekend.

Sharon Bortle was a teacher at the school for 13 years.

"This is a huge, huge loss," Dale Horner, school principal, said. "Tough is a very, very tough concept for little guys, and we're just going to try to get them through it."

Horner said Sharon Bortle always wanted what was best for the children at Durand Elementary.

"Durand is a family, a very, very tight school, and when you lose anybody, it's tragic, but when you lose somebody like Sharon, it's even harder to take," Horner said.

The Bortles' 9-year-old son is in a different fourth-grade class at the same school where his mother taught.

"Her son was here so we're not only missing Sharon; we're looking at the impact this is going to cause on a 9-year-old little boy," Horner said.

A neighbor said she heard the gunfire Sunday.

"I heard a loud bang, like a shotgun, and I stopped for a second and heard a scream. After that, maybe a few minutes later, I heard another shot," Iris Ortiz said.

Police said Frank Bortle shot himself in the face when he saw police approaching. He is being guarded by police and was charged with homicide.

"This is an unimaginable tragedy for our school district family," district spokesman John Sbrana said. "Our thoughts and prayers are with the families."

"She was a wonderful teacher and a really wonderful woman," Sbrana added.

More than a dozen grief counselors and social workers were on hand at the school Monday to help staffers and children deal with the tragedy.

"We've brought in counselors from many other buildings for support," Linda Santagata, a grief counselor, said. "You talk about the passing. You talk about the fact that they have memories of her, that it's wonderful to be able to reach out to her family to support them."

The couple had recently separated, and police said they believe the shooting may have been prompted by an argument about time spent with the children. Police said the couple's relationship had taken a violent turn less than two months ago.

Horner said Sharon Bortle never said a word about trouble brewing at home.

"Sharon's not that kind of person. Sharon's always got a smile on her face, always caring about other people," Horner said.

In December, Sharon Bortle had obtained a restraining order against her husband after he allegedly beat her during an argument regarding Christmas shopping, police said. However, the restraining order was later dismissed in court, although it's unclear why.

Police arrested him, and he was charged with simple assault after that incident.

Police also seized nearly 20 of his weapons in December, and Frank Bortle surrendered his Firearms Purchasers ID Card. He was released on bail pending a court hearing in that incident.

Investigators are trying to figure out how he obtained the weapon he allegedly used in the slaying but it was not one of the weapons seized at that time.

Frank Bortle's father did not wish to comment.