RIYADH, 15 June 2004 — The son of the American electronics engineer who was kidnapped Saturday in Riyadh has pleaded with his captors to release him.

“Let him go,” said Paul Johnson III, the hostage’s eldest son. “It’s not his fault we’re over there. It’s not his fault we had to go there. It was his job,” he pleaded in an interview with the Florida-based Bradenton Herald.

Paul M. Johnson was reported missing from Saturday evening in apparently kidnapped by militants here, who posted late Saturday on an Islamist website several of Johnson’s identification documents.

The statement threatened to treat Johnson as US troops treated Iraqi prisoners — an apparent reference to abuses at Abu Ghraib prison in Iraq.

Johnson, 49, an employee of Lockheed Martin in the US, had worked in the Kingdom for 12 years and was contracted to Advanced Electronic Systems to develop radar systems for Apache helicopters in the Kingdom.

An employee of the same company, Kenneth Scroggs, was killed on the day Johnson was abducted. Scroggs was shot in the back outside his home in a residential neighborhood in the afternoon.

Security forces in cooperation with the US State Department are looking for the culprits but have so far come up empty-handed in any of the attacks on Westerners since the Alkhobar killing spree and hostage drama.

“They don’t really know much about it right now,” Paul Johnson III, 28, said. “They said that they are trying to follow leads.”

The younger Johnson said he spoke to his father last weekend and although he expressed concerns about the mounting violence in the Kingdom, he did not say anything about being worried about his own safety.

Paul Johnson Jr. was supposed to return to the United States this month for a visit, but the trip was pushed back until the fall, the son said.

“My father ... has always been nervous about being there,” Paul Johnson III told NBC News. “But over the years of being there, you pump your gas at the same place. You get your coffee at the same place. You just get into routines and I think that’s just what happened to him.”

Johnson’s son, a drywall contractor, said he hadn’t seen his father since 2000 but kept in regular touch with him through e-mails and telephone calls.

Paul Johnson Jr. has never met his three-year-old grandson, who was named after him.

“He’s probably praying,” Paul Johnson III said of his father. “He’s probably wondering how he got himself in this situation and wondering how he can get himself out of it.”

Johnson’s family in New Jersey was devastated, said Barbara Pagliughi, a home health aide for his 67-year-old mother. “They don’t know what’s going on. They learned through the media.”

“Nobody came and contacted them. Nobody knows where he is, whether he’s alive or not.”

Pagliughi had told the paper that she had spoken on the telephone with Paul Johnson Jr. three weeks ago.

She also spoke with his wife, a native of Thailand. She said the two were building a home in Thailand.

In Stafford Township, Johnson’s mother, Delores, and brother, Wayne, awaited word.

“I just don’t want to hear bad news because I know the captors are sadistic,” said his brother, Wayne Johnson, 48, who spent yesterday watching television news at his home. “The more people know about it then maybe they can get him out safe,” he said.

Lockheed Martin released a statement Sunday saying it believed “Johnson has been kidnapped, but we have no information on his status or whereabouts. We will continue to work with the US and Saudi government and military officials and the family of Mr. Johnson to provide any assistance possible. Our thoughts and prayers are with Paul Johnson and his family.”