A man has been charged with causing unnecessary suffering to animals in Northern Ireland.
The 23-year-old is due to appear at Craigavon Magistrates' Court on Wednesday.
A 16-year-old male teenager has been released on bail, pending further police inquiries.
All charges will be reviewed by the North's Public Prosecution Service (PPS).
Police say they believe the incident happened on Saturday in Lurgan.
They are appealing to anyone who may have seen footage on Snapchat or other social media platforms to contact them.
The PSNI released this photo of Sparky | Image: Facebook/PSNI Craigavon
Craigavon PSNI say: "If you have seen any footage or photographs of the incident (not just screen shots of conversations and allegations) then we need to hear from you.
"If you happened to screen shot or record any videos that were sent, we need them.
"That will be the difference between a evidential case and pure hearsay."
The statement adds: "Whatever happened, it is obvious that little Sparky suffered a horrendous death.
"We want to get to the bottom of that and make sure that whoever is responsible is held to account."
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PSNI chief inspector Jon Burrows says police "responded quickly" to reports alleging an 11-week-old puppy had been killed with a hammer.
We responded quickly to reports yesterday evening alleging an 11 week old puppy had been brutally killed in Lurgan with a hammer. We have arrested two male suspects aged 23 & 16 and recovered the remains of the little dog & a hammer. An very through investigation is on going.
— Jon Burrows (@PSNICIJBurrows) February 6, 2018