The Division of State Fire Marshal investigators said a fire that killed a man and his three sons was intentionally started.

Ulrick Estimot, 37, died in the blaze along with his three sons: Trey, 11, Terrell, 7, and Trenton, 5.

The children's mother, Angela Latshaw, said, "They were just smiling, always happy. My 5-year-old loved to put a smile on somebody's face. The 11-year-old … they just all just loved to make people smile."

Shane Cartmill, public information officer for the Division of State Fire Marshal, said details of the fire investigation have been turned over to the East Liverpool Police Department, which will investigate the incident as a crime. State Fire Marshal investigators will support the police department as needed throughout the investigation.

In a news release, Cartmill said, "As this is an ongoing criminal investigation, specific details about how and where the fire was set will not be released at this time. Investigators are waiting on additional information from the coroner's office."

Fire Chief William Jones said Latshaw called in the fire at 12:03 a.m. Saturday.

The father was found on the first floor with his 5-year-old son, and the other two boys were found on the second floor, according to the Columbiana County Coroner's Office. The coroner says all four suffered burns and inhaled high levels of carbon monoxide.

"We have theories that we're working on, and until that evidence comes back, they're just theories. We have no conclusive evidence," Jones said.

The arson investigation is being conducted by the Division of State Fire Marshal, the Columbiana County Coroner's Office, the East Liverpool Police Department and the East Liverpool Fire Department.

"Any time you have a fire, it's serious. Any time you have an injury it makes it that much more important. When you have fire deaths, especially at the hands of someone, it's something that we need to look into as deeply as we can," Cartmill said.

A candlelight vigil that was scheduled Monday night for the family has been canceled. Stay with NEWS9, WTOV9.com and WTOV9 Mobile for continuing coverage.