The 17-year-olds were found by police at Huntcliff in Saltburn on Friday evening.
The closure will save the Darlington council more than £300,000 a year.
The rifle is thought to be used in paintballing games, police said.
Parts of northern England are affected by wintry weather.
High-profile cases of animal cruelty have provoked public outcry over apparent leniency. Is the law tough enough?
Substitute Kyle Vassell scores a late winner as Blackpool beat Hartlepool to move into the League Two play-off places.
Middlesbrough defender Ben Gibson is called up to the England squad for the first time after an injury to Manchester United's Chris Smalling.
Darlington & Stockton Times
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