WAYLAND (CBS) – What could cause 18-year-old Nathaniel Fujita, college-bound and without a prior criminal record, to allegedly murder 18-year-old Lauren Astley?

A domestic violence expert told WBZ-TV that sometimes, warning signs are subtle.

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“They only care about that one other person, that they want to know where that person is all the time,” said Laura Van Zandt.

Van Zandt runs a domestic violence outreach program that talks to students. Last year, her group was at Wayland High School speaking to juniors, including Fujita and Astley.

WBZ-TV’s Diana Perez reports.

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In court, prosecutors revealed the high school grads broke up recently.

On Sunday when Astley went missing, Fujita told police she came to see him and stayed only a few minutes without her car.

But, prosecutors say Fujita killed Astley, strangling her to death with bungee cords. It’s a common crime of passion in domestic violence cases, according to Van Zandt.

“Strangling is a very intimate way of killing somebody. You use your own hands and you hold onto them until they stop moving,” said Van Zandt.

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Both teens were headed to college next year. Van Zandt says that can cause anxiety in young relationships and it’s a time when parents should talk to their teenagers.