A Utah man is suspected of killing a man in Los Angeles and then shooting an off-duty sheriff’s deputy in the head in what his family called a “horrifying and senseless attack.”

Rhett Nelson, 30, was arrested Tuesday in Long Beach, Calif., after he used a phone in a Long Beach church to call his father in St. George.

“He referred to committing murder in southern California,” Los Angeles County Sheriff’s Capt. Kent Wegener said at a news conference Tuesday. In fact, said Los Angeles County Sheriff Alex Villanueva, “He referenced that he killed two.”

At the time Nelson called his father, a manhunt was underway for a gunman who on Monday shot Los Angeles County Sheriff's Deputy Joseph Gilbert Solano, who was off-duty and visiting a Jack In The Box restaurant in Alhambra, Calif., when someone shot him in the head, said Los Angeles County Sheriff Alex Villanueva. Solano is on life support and "in grave condition," Villanueva said.

The description of the shooter, and the shooter's car, matched reports of another shooting about an hour earlier on Monday, in the central Los Angeles community of Newton, said Los Angeles Police Chief Michael Moore. A motorist pulled up to a man and, after a "brief exchange ... gunfire erupted," Moore said. The victim, a 30-year-old man, later died.

Police were searching for the shooter in both attacks when Nelson's father called investigators on Tuesday afternoon to report what Nelson had said. He also provided the phone number of the church Nelson had called from.

Nelson's family had been searching for him for about two weeks and had reported his disappearance to St. George police, officers there confirmed. On May 30, Nelson's father, chiropractor and author Bradley Nelson, posted on Facebook that his son had disappeared three days earlier, taking only his phone and a white Kia Sorento — the vehicle seen at both shootings in California.

(Sarah Reingewirtz | The Orange County Register via AP) Los Angeles County Sheriff Alex Villanueva speaks during a news conference in Los Angeles on Tuesday, June 11, 2019. Rhett Nelson, 30, of St. George, Utah, was arrested Tuesday on suspicion of shooting an off-duty Los Angeles County sheriff’s deputy at a fast-food restaurant Monday, and authorities say they are investigating whether he may have killed another man an hour earlier in attacks that both appear to be random.

“We’ve had no contact with him, his phone is dead or off since then,” the father wrote. “He has a history of opiate abuse and has been clean for about 6 months, but we know what a terrible struggle that is. We are praying for his safe return.”

On Wednesday, June 5, the Nelson family reported getting a brief phone call from Rhett Nelson but posted no further updates before Tuesday, when he called from the Long Beach church.

Officers went to the church, where the Kia Sorento was leaving. They executed a "tactical stop" and arrested Nelson, who was driving, Wegener said.

Inside the car, officers found a fedora and a maroon shirt that matched what the shooter at the Jack In The Box was seen wearing. They also found a revolver "matching the gun used in the assault" on Dep. Solano, Wegener said.

Moore and Villanueva said they could not discuss possible motives in the shootings and said they were still conducting interviews with Nelson and with witnesses tied to both attacks.

Nelson has no violent criminal history in Utah. In 2014, he pleaded guilty to driving with a measurable amount of controlled substance in his body in Salt Lake City, and he pleaded guilty and no contest to underage alcohol offenses in 2007. Two other drug cases were dismissed at prosecutors' requests.

Solano, 50, is a 13-year veteran of the Los Angeles County Sheriff's Department. He was taking his mother's car in for service at an Alhambra Jiffy Lube when he stopped into the Jack In The Box on Monday, Villanueva said.

He is "definitely a family man," Villanueva said. Solano's father died a few months ago and he is "the sole provider for his mother," Villanueva said.

"He definitely [is] a kind-hearted, generous person, always willing to help others before himself," Villanueva said.

Moore did not identify the victim in the Newton homicide.

In a prepared statement on Tuesday, Bradley Nelson wrote:

“My wife, Jean, and I — along with our family — are saddened beyond words to hear of the shooting of Los Angeles Sheriff’s Deputy Joseph Solano, and to learn that our son Rhett is being held in connection with this horrifying and senseless attack. Rhett has been missing since May 26, 2019, leading us to file a missing person’s report with authorities. We have spent much time and effort in an attempt to help Rhett and bring him home safely, and we have been distraught and worried since his disappearance. We are cooperating fully with authorities and will provide them with all information they request concerning Rhett and his struggles. We ask that people please pray for Deputy Solano and his family.”