Infiltrator?

What does infiltrator mean in this JTA headline, Israeli troops shoot, kill Palestnian infiltrator. Now see the report from Reuters in Ma'an News Agency:

Israeli soldiers shot and killed a 20-year-old Palestinian man who approached a fence near Gaza's border with Israel, medics said on Monday.

An Israeli military spokeswoman confirmed the shooting took place after darkness fell on Sunday, saying troops opened warning shots when a man walking in a riverbed failed to heed orders to leave the buffer area.

Palestinian medics said the victim, Ahmad al-Nabaheen, was unarmed and mentally unfit. 

Medics had to wait around six hours for permission to pick him up from the spot near al-Bureij refugee camp. They suspected he died of injuries for which he might have been treated.

A Palestinian gets killed for approaching a fence in Palestine?  Some infiltrator.