How to split a paired-end FASTQ file into two separate FASTQ files (forward and reverse)?

I have to analyse a paired-end DNA-seq read that are in an unusual format: both pair-end reads are joined in one FASTQ. I already obtained this file by reverting from BAM file to FASTQ. So, I need to split the file in two separated FASTQ paired-end files. Any comment or suggestion would be appreciated. I know that there is a galaxy tool named FASTQ splitter that can do this for RNA-seq read but not sure this could work for DNA-seq read as well. Thanks