''We strongly suspect he was intentionally returned.''
The hutch and bowl were still missing.
To remove Thomas' damaged eyeball would cost up to $1000 so the family made the difficult decision to euthanise their pet.
The loss of Thomas had been ''upsetting and confusing'' for her children, Freya, 13, Aila,11, Felix, 9, and Amos, 5.
''We had kids crying with sadness on Monday and then crying with joy on Tuesday.''
The family were upset Thomas would be put down today but were grateful to have the extra days with him.
The theft was ''unsettling'' because someone had the audacity to steal from the close community in the quiet cul-de-sac, Pettigrew said.
Senior Sergeant Ben Butterfield said as well as the guinea pig, two rabbits were stolen from a Leithton Close property overnight on June 9.
The thieves returned the following night and stole two more.
In a third theft at the address, the rabbits' cage was stolen on Tuesday night.
''Obviously, this is pretty strange,'' Butterfield said.
Police suspected the addresses had been targeted.
''It's obviously a concern for us that someone is out there taking people's pets.
''We would suspect that because these two lots of animals have been taken in such close proximity that someone is targeting them,'' Butterfield said.
''Therefore, we believe that someone must know something about this because these animals have been stolen to order or stolen for purpose.
It was obviously distressing for the families and children involved, he said.
If you know anything about the animal thefts, contact Dunedin police on (03) 471 4800 or Crimestoppers on 0800 555 111.
- Additional reporting by Timothy Brown
