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North Park Elementary School in San Bernardino will remain closed as police continue to investigate why a 53-year-old Riverside man opened fire in a special education classroom the day before, killing his estranged wife and an 8-year-old student and then turning the gun on himself.

A second student wounded in the attack, a 9-year-old boy shot in the upper body, was doing well and in improving condition, San Bernardino Police Department Chief Jarrod Burguan said Tuesday.

Cedric Anderson is shown in a photo provided by San Bernardino police on April 10, 2017.

Burguan provided an update during an 11 a.m. news conference, giving new details, including that gunman Cedric Anderson of Riverside fired 10 rounds at a range of 10 to 15 feet away from his wife.

Anderson checked in at the school office and proceeded to his wife’s classroom, B-1, just before 10:30 a.m. Without saying anything, he unloaded a .357 Smith & Wesson revolver that was sold in 1979 in Michigan, Burguan said. The firearm was not sold to Anderson and no further records for the gun are available.

Anderson’s wife, 53-year-old school teacher Karen Elaine Smith, died at the scene. Two students near her were also shot by apparently errant rounds and were rushed to Loma Linda University Medical Center.

Officials later announced one of the boys, Jonathan Martinez, had died.

Anderson reloaded at least once during the attack before shooting and killing himself, Burguan said.

Fifteen students between first and fourth grades were in the special education classroom, as were two adult aides.

Investigators learned that the couple had been in a relationship for four years and had married in January. In March, marital problems developed and Smith moved out of their Riverside home and was living with her adult children, Burguan said.

There was an allegation of infidelity, Smith’s relatives told police, but Burguan said that hadn’t been verified.

Smith told family that Anderson was behaving oddly and had made threats toward her, the chief said. He had been reaching out to her to get attention, she thought, Burguan said.

She was resistant to his efforts to get her to return home.

“I don’t know if that just reached a boiling point or what it was, nor do we know exactly why he chose to do this at the school,” Burguan said.

Nobody at the school knew about the marital discord, and there was no reason to suspect a violent crime would occur, Burguan said.

“She effectively kept her private life private,” the chief said.

The school had properly followed its policies, both Burguan and San Bernardino City Unified School District Superintendent Dale Marsden said Tuesday. The district will complete an “after-action review process” to examine what happened, Marsden said.

No suicide note has been found, though investigators discovered a handwritten document indicating that Anderson was “feeling disrespected” and seeking closure. If he hadn’t gone on to open fire, there would be no reason that the note would raise alarm, Burguan said.

“In this case, we don’t see anything that has come to our attention that says we should have known or we should have seen this coming,” the chief said.

Smith, a resident of Riverside and Moreno Valley with four adult children, was a special needs teacher employed by San Bernardino City Unified School District for the last 10 years. Most of her career was spent at Cajon High, Burguan said.

Grief counselors are available to North Park Elementary School students, parents and staff Tuesday, the Los Angeles Times reported.

A candlelight vigil was at the school at 7 p.m. Tuesday.

Karen Smith is shown in a photo provided by San Bernardino police on April 10, 2017.

At the news conference, Marsden said that the school would be closed until Monday, April 17. North Park parents who need child care Thursday and Friday can take their students to Del Vallejo Middle School.

Burguan said Monday that Anderson had a criminal history, including domestic violence, weapons and possible drug charges. On Tuesday, Burguan said the shooter had been arrested four times between 1982 and 2013, but was never convicted of any charge.

The most recent arrest was around the time that he and Smith began their relationship, but it’s not clear if the arrest was related to her. In the case, Smith was arrested on suspicion of assault and weapons charges that did not involve a gun, Burguan said.

Anderson was unemployed at the time of the shooting but had worked as a maintenance man and a pastor at a church in the Las Vegas area. He has three adult children.