Young, in love, engaged to be married, and ready to kill Americans.

Add “fiancé visas” to the list of ways suspected terrorists have gained legal entry into the United States.

Tashfeen Malik, one of the alleged shooters in Wednesday’s San Bernardino, California, massacre, reportedly came into the United States on a K-1 visa available to foreigners who are engaged to marry American citizens. State Department statistics indicate the government has issued nearly 30,000 a year, on average, over the past five years.

Although far less commonly abused than other avenues of entry — such as student and tourist visas — the K-1 visa is potentially more vulnerable, experts warn.

The State Department said federal authorities in fiscal year 2014 turned down just 118 out of the 36,543 applications received for K-1 visas. That is an acceptance rate of 99.7 percent, on par with the rate of NATO officials gaining entrance under special visas for officers of the military alliance.

“A denial rate that low suggests one of two things: Either it is a magnificently honorable population or somebody’s being casual in their screening,” said David North, a fellow with the Washington-based Center for Immigration Studies. “Uncle Sam loves Cupid.”

Foreigners engaged to Americans have been considered “fair-haired children by State Department, or people doing the interviews overseas,” North said.

Law enforcement authorities say that Malik, 27, and husband Syed Rizwan Farook, 28, fired 75 rounds at a holiday party for Farook’s fellow county workers. They later died in a shootout with police.

The American-born Farook met Malik through an online dating site, and they got to know each other in Saudi Arabia, according to the Los Angeles Times. Law enforcement officers said they believe Malik radicalized her husband.

Under the law, a K-1 visa holder has 90 days to get married after coming to the United States. Applicants must submit to fingerprinting and provide police certificates from countries where they have lived for at least six months and undergo an interview by consular officers.

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Drug trafficking, overstaying a previous visa and submitting fraudulent documents are some of the things that trigger a denial.

While there is no evidence Malik committed fraud in obtaining a “fiancée visa,” experts said Malik’s application process likely will be scrutinized over the coming days.

“Should there have been things that the government should have seen?” asked Jessica Vaughan, director of policy studies Center for Immigration Studies.

That scrutiny already has begun. Sens. Jeff Sessions, R-Ala., and Ted Cruz, R-Texas, demanded that the Obama administration release detailed information about the immigration histories of the San Bernardino shooters.

“The security task involved is immense, and Congress must have the requested information if lawmakers are to act as responsible stewards of American immigration policy,” the senators wrote in a letter to administration officials.

Although fiancé visas until now have been little-used by terrorists, a related method — marriage fraud — has been documented. A 2005 report by CIS highlighted 16 terrorists who extended their stay in the United States, often by marrying Americans.

 “It would be a mistake to say these people are put through some sort of background wringer.”

Vaughan, a former foreign service officer, said it is important to recognize that U.S. officials reviewing applications for non-immigrant visas examine records, but do not conduct full-blown background checks.

“The green card and visa review process is already susceptible to fraud,” she said. “It would be a mistake to say these people are put through some sort of background wringer.”

Vaughan said consular officials have a “crushing workload” that prevents anything more thorough.

“The Obama administration has totally relaxed the review process and put a lot of pressure on them to approve pretty much everything … They’re told to get to ‘yes,’” she said.

North said K-1 visas are preferable to immigration for people wanting to come into the country, because the process usually is faster. And once married, Vaughan said, the path to citizenship is faster — three years instead of five.

“Terrorists have exploited just about every visa program to get into this country,” she said.