Ammen, 44, and Spiridon, 42, were residents of San Carlos. They died in the collision and their 7-year-old twin daughters were injured, as were two passengers in the teen's car.
The 17-year-old was arrested on Nov. 18 and booked into the San Mateo County Youth Services Center after spending two weeks at Stanford Hospital, according to officials. Harrison was arrested at his residence on Nov. 21 and was booked into the San Mateo County jail, police said.
A police investigation determined that Harrison and the teen were engaged in a speed contest that caused the fatal crash. The drivers are facing two counts of second-degree murder each and, if convicted, could serve 15 years to life in prison, police said.
San Mateo County District Attorney Steve Wagstaffe also had considered filing the lesser vehicular manslaughter charge. A misdemeanor vehicular manslaughter conviction carries a sentence of up to one year in county jail; a felony conviction means the driver could face up to six years in a state prison.
Whether the teen had been drag racing is "an important element" in determining the appropriate charges, Wagstaffe said last week.
Ammen and Spiridon were Palo Alto High School graduates who had met in middle school and become "high school sweethearts," one family member said.
The couple lived with their daughters in Eaton Hills, according to Gregory's younger brother and the girls' uncle, Michael Ammen. Gregory Ammen was an audio engineer at Dolby, and Spiridon was a Google employee.
Ammen and Spiridon "loved their daughters more than anything in the world," according to Michael Ammen, who said the couple also enjoyed hiking, biking, live music and exploring the outdoors.
"Greg always put Grace and his family first," Michael Ammen said, describing his brother as "a source of kindness and light and love in the world." The couple, known as 'The G's' by their friends, "were the light of every party they went to," he added. "They were social magnets bringing people from all over (work, school, wherever) together for fun."
Maura McCarthy, a longtime friend of Spiridon's, described a mutual crush between Spiridon and Ammen and several dates between the two that blossomed after college and grew into a lifelong partnership, admired by friends and family alike.
"They really held each other in such high esteem and regard, and it was really nice to see — a model relationship for me," McCarthy said.
A GoFundMe organized by Spiridon's sister, Liza Spiridon, has raised more than $530,000 to support the twin daughters.
"The world lost two beautiful souls, and leaves two amazing girls without parents," Liza Spiridon wrote on the fundraiser page. "We would like to honor them by setting up resources for the care of their wonderful 7-year-old girls."
Redwood City police are asking that anyone who has information about the criminal case call the department's tip line at 650-780-7107.
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