The male was taken into custody on 3 May, having been arrested in connection with the incident at the garage in the early hours of 30 April where a staff member was hospitalised, amid an attempt to break into a safe on the site.
It’s being treated as an aggravated burglary.
Guernsey Police want to speak to anyone with information as part of continuing enquiries, “particularly if you were in the area at the time or have dash cam or CCTV footage.
“This was a particularly violent offence, which took place at Vale Service Station between 03:30 and 03:45 on Tuesday 30 April, and Crimestoppers is offering a reward of up to £750 for information leading to the arrest, charge and conviction of the offender,” said a police spokesperson.
“Anyone with information is asked to call police on 01481 222222 or Crimestoppers anonymously on 0800 555 111.”