My snide comment on the article aside, the question is answerable, but first I'd just like to fix the original sentence a bit...
A man in his 20s was arrested in connection with the incident and has since been released pending further enquiries.
Whoever wrote it has obviously been reading newspapers to gain their experience at "reporter police-speak" but didn't fully understand it, I think.
The entire passage is written in "reporter police-speak" These are terms used frequently in this type of reporting.
To break it down
A man was arrested.
There was sufficient suspicion he was involved, so the arrest was "in connection with the incident"
He was released afterwards.
This is only going to happen under two circumstances.
- He was 'bailed' or 'arraigned' to later appear in court.
- There wasn't enough evidence to hold him any longer.
'Since released' means he was released sometime later. It doesn't specify when precisely.
'pending' is simply 'awaiting a decision or conclusion'. In "police speak" 'pending further enquires' means they need to gather more evidence as there isn't yet enough to charge the suspect.
Being arrested is not the same as being charged with an offence.
You can be arrested on suspicion of something, but to be charged the police must be reasonably certain they have sufficient evidence to support their claim.
Once arrested, the police can only hold a suspect without charging them for a limited time (I think it's 24 hours, but I'n not a lawyer, I just watch a lot of police shows ;)
After that he must be either charged or released.
BTW, the bit I snipped out - under investigation - is just tautological.
The incident is under investigation, enquiries are being made.
The man may or may not be charged once the investigation/enquires are completed.