Wow, he was going to be sentenced on July 9th for those gun-related charges.
I found the Case # in Vista through a court index search, but still don't know the actual gun-related crime.
Found this too.
http://www.utsandiego.com/news/2014/jun/21/belvedere-flint-arrest-mercado-shooting/
"According to jail records, Mercado previously was arrested on April 29 and booked into county jail on gun-related charges. Court records show he was charged on May 5 in Vista Superior Court. The nature of the case was not immediately available."
bbm
I could be wrong but I think maybe when they got him and the gun on April 29, since it was a felony they could get a swab for DNA and possible ballistic match to bullets used in the killings. IIRC he plead guilty so must have bonded out until sentencing. In the meantime LE connected some dots. And maybe even lined him up with video surveillance from that night and a car match.
But apparently they interviewed him for nearly 8 or 9 hours, between the arrest time and the booking time. Perhaps the delay in first arraignment is to allow time to act on information learned from the interview. I'm sure going through his cellphone records will be a real party for LE.
JMO's