vigilant, vigilante

Vigilant or vigilant ( vidge ih lent ) means watchful, or paying close attention--
We hope the new foreman will be vigilant in his search for safety violations.
It is important to be vigilant, especially on the night shift. Check these monitors every 60 seconds.

Vigilante or vigilante ( vidge ih lantee ) means someone not officially a law enforcement official, who fights law breakers; someone who takes the law into his or her own hands--
The mayor worried that a vigilante would take over, if the suspect was not caught.
They liked to watch the old western series about a vigilante who saved people from outlaws.

Now that you know that, you can say--
"The police were vigilant in their search for the vigilante who had been towing away illegally parked cars."

Note--"vigilance" means a state of being watchful or on the alert--
His vigilance paid off; he got a picture of the creature that had been making noise in the yard at night.
Note # 2--"vigilantes" ( vidge ih lant teez ) is the plural ( more than one ) of "vigilante", meaning someone who has decided to take the law into his or her own hands--
They styled themselves internet vigilantes, and hacked sites they thought didn't follow the rules.
Note#3--a "vigilance committee" is a group of vigilantes, who have decided to enforce the laws themselves, and to ignore the police and other law enforcement officials.