Some years, the US has seen more than 10,000 people killed by guns.
Practically every year since the 60s, I think.
The US homicide figures are often misrepresented. The FBI gets reports from local police forces. Usually those reports include details of the victim, method of killing, probably reasons (where known) etc. However, not all homicide reports come with that supplemental detail.
The FBI publishes the overall figure, and also the figures broken down into weapons, race, motive etc. However, the figures are raw figures only, and don't take into account the homicides for which they have no supplemental data.
For 2002, the FBI lists 16,204 homicides (not counting negligent homicide)
However, when you look at the detailed table, Murder Victims by Weapon, they show a total of 14,054 homicides, 9369 by firearm. That's a rate of about 66% murdered with a firearm. If you apply that 66% to the total figure, including those where the FBI haven't been informed of the method of killing, you get 10,694 homicides with a firearm.
Note, this does not mean counting deaths where the cause is uknown or unclear, only homicides where the cause, along with other details, hasn't been reported.