Installing security bars on windows on rental in LA?

[Sheila Bee]

Hi all, I have a rental property (SFH) in mid city LA. It's an up and coming area but still very urban with a fair amount of crime. Last weekend, my tenants had a trespasser who jumped the security fence and pounded on the window at 2 am before running away after the tenants' dog started barking. Police were called and didn't find anything, not surprisingly. It turns out one of the bars in the fence was slightly loose, so I had that fixed the very next afternoon, but the repairman mentioned to the tenants that perhaps bars could be installed on the windows (no idea why he told them that). I have seen such bars on other houses in the neighborhood, but I'm reluctant to install them for a few reasons. On the flip side, I definitely want my tenants to feel safe and I especially don't want a lawsuit down the line should a break in happen. Any suggestions on how to proceed? The tenants do have ADT installed and are putting up more cameras. Also, if anyone has recommendations on someone who does this kind of work in LA (inexpensively) I would love to hear them. Thanks in advance!