Firstly, Sorry my english is not that good.
I don´t know what decade this movie was made. Probably 80s. Things I remember about this movie:
1. Some bad guys take family hostage (don´t remember reason why), only youngest son somhow escapes and is hiding in the house.
2. One guy he kills, is sitting behind table and doing something on PC. Kid pours water on carpet under him and electrcute the bad guy.
3. Other bad guy is patroling next to swimming pool, smoking. Kid pours lighting fluid (not sure about this) into water gun and hit the cigarette, setting the bad guy on fire.