Two days after a mass shooting at a child's birthday party in Stockton, law enforcement is making promising progress in the investigation, the San Joaquin County sheriff told NBC Nightly News.

"We're making progress on this and getting closer and holding not only the ones that actually did the shooting responsible, but anyone that had anything to do ahead of this and afterwards, either in the planning of it, or trying to cover it up, to be held accountable," Withrow told NBC News Correspondent Steve Patterson.

He said he believes there will be a resolution "very quickly," but that deputies were also being very thorough.

"This didn't happen in a vacuum," Withrow said. "We had people that helped them set this up, people that knew this was going to go down. And then after it happened, thes

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