Police probe how 10-year-old boy got gun

[petronius]

1. Current CA law with regard to firearm storage looks like this:

25100. (a) Except as provided in Section 25105, a person commits
the crime of "criminal storage of a firearm of the first degree" if
all of the following conditions are satisfied:
(1) The person keeps any loaded firearm within any premises that
are under the person's custody or control.
(2) The person knows or reasonably should know that a child is
likely to gain access to the firearm without the permission of the
child's parent or legal guardian.
(3) The child obtains access to the firearm and thereby causes
death or great bodily injury to the child or any other person.
(b) Except as provided in Section 25105, a person commits the
crime of "criminal storage of a firearm of the second degree" if all
of the following conditions are satisfied:
(1) The person keeps any loaded firearm within any premises that
are under the person's custody or control.
(2) The person knows or reasonably should know that a child is
likely to gain access to the firearm without the permission of the
child's parent or legal guardian.
(3) The child obtains access to the firearm and thereby causes
injury, other than great bodily injury, to the child or any other
person, or carries the firearm either to a public place or in
violation of Section 417.


25105. Section 25100 does not apply whenever any of the following
occurs:
(a) The child obtains the firearm as a result of an illegal entry
to any premises by any person.
(b) The firearm is kept in a locked container or in a location
that a reasonable person would believe to be secure.
(c) The firearm is carried on the person or within close enough
proximity thereto that the individual can readily retrieve and use
the firearm as if carried on the person.
(d) The firearm is locked with a locking device, as defined in
Section 16860, which has rendered the firearm inoperable.
(e) The person is a peace officer or a member of the Armed Forces
or the National Guard and the child obtains the firearm during, or
incidental to, the performance of the person's duties.
(f) The child obtains, or obtains and discharges, the firearm in a
lawful act of self-defense or defense of another person.
(g) The person who keeps a loaded firearm on premises that are
under the person's custody or control has no reasonable expectation,
based on objective facts and circumstances, that a child is likely to
be present on the premises.

http://www.leginfo.ca.gov/cgi-bin/displaycode?section=pen&group=25001-26000&file=25100-25130

Assuming that the gun owner was a family member of the girl, and chose to keep the gun in the garage - which seem like likely guesses - I think the only reason not to file charges would be 25105b or 25105d. If there was some sort of un-reported locking container or device that the children broke...