A 17-year-old organizer of an outdoor party in Avondale that turned fatal Dec. 3 testified Thursday that he recognized a white Explorer when it pulled up to the gathering, and he quickly asked the occupants to leave because rival gang members were present.

The Kennett High School student said the Sur 13s, also known as Surenos, complied but returned with another carload an hour and a half later. He described a chaotic scene as weapon-wielding Sur 13s confronted members of the Vikings, and frightened partygoers scattered in all directions.

The testimony came during back-to-back preliminary hearings for James L. Jones, 19, and Stephen A. Daddezio, 17, both of West Grove. District Judge Matthew Seavey ruled that sufficient evidence existed to hold both for trial on all charges related to the deaths of Cuahuctemoc Bedolla, 27, and Jose Rodriguez, 29, both of West Grove.

Jones is accused of killing Bedolla. Daddezio is accused of participating in the murder plot.

New Garden Township Police Sgt. Joseph Nangle testified that Jones, who was represented by Assistant Public Defender Meredith Copeland, told him he was "knocked to the ground" during the fight, took out a knife, and stabbed an individual three times. It was recovered at the scene, Nangle said.

Chester County Detective Robert Dougherty testified that a man affiliated with the Vikings saw Jones and Daddezio the day after the killings and tried to confront them, but they fled. In the process, Daddezio, an Avon Grove High student, stumbled and dropped his cellphone, which ended up with investigators.

Defense attorney Mark Rassman argued unsuccessfully that prosecutors could not trace the incriminating messages recovered on the phone, including a reference to the killings, to Daddezio because he had lent the phone to Jones.

For security reasons, the hearing was held at the Justice Center in West Chester rather than at Avondale District Court. Deputy sheriffs, including a K-9 unit, monitored the proceeding.

Nangle testified that the investigation began when officers responded to Jennersville Regional Hospital in West Grove at 11 p.m. Dec. 3 for a report that Bedolla was critically injured from apparent knife wounds. Bedolla was flown to Christiana Hospital, where he was pronounced dead.

Detectives then visited the 1600 block of Baltimore Pike in Avondale, a remote residential-industrial area where the fight had erupted. Chester County Detective Gerald Davis Jr. testified that Rodriguez's body was found the next morning. He said investigators widened the search for evidence after Rodriguez's relatives expressed concern that he had not returned home.

Police said gang tensions have plagued the area for more than a decade. The largest local Hispanic gang is the Sur 13s, a national group believed to be an offshoot of the Mexican Mafia. Two smaller gangs - the Vikings and the Ochos - often combine their resources to confront the Sur 13s.

Authorities said the Vikings originated in southern Chester County to combat the Sur 13s. "Sur 13" is Spanish for South 13, a reference to Southern California and the 13th letter of the alphabet. Those who study gang patterns believe the M stands for marijuana in some groups, mafia in others.

The fact that neither defendant is Hispanic does not preclude involvement in the gangs, police said, adding that the investigation is continuing.

Contact staff writer Kathleen Brady Shea at 610-696-3815, kbrady@phillynews.com, or @brandywinebits on Twitter. Read her blog, "Chester County Inbox," at www.philly.com/chescoinbox.