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Sgr B2 is a well-known star forming molecular cloud complex in the Galacticcenter region showing evidence of high energy activity as traced by theK$\alpha$ neutral FeI line at 6.4 keV, as well as GeV and TeV $\gamma$-rayemission. Here we present VLA and GMRT observations with respective resolutionsof $\approx3.5"\times1.2"$ and 25$"\times25"$ and report the detection of anOH(1720 MHz) maser, with no accompanying OH 1665, 1667 and 1612 MHz maseremission. The maser coincides with a 150 MHz nonthermal radio source in SgrB2(M). This rare class of OH(1720 MHz) masers or the so-called supernovaremnant (SNR) masers, with no main line transitions, trace shocked gas andsignal the interaction of an expanding SNR with a molecular cloud. We interpretthe 150 MHz radio source as either the site of a SNR -- molecular gasinteraction or a wind-wind collision in a massive binary system. Theinteraction of the molecular cloud and the nonthermal source enhances thecosmic-ray ionization rate, allows the diffusion of cosmic rays into the cloudand produces the variable 6.4 keV line, GeV and TeV $\gamma$-ray emission fromSgr B2(M). The cosmic ray electron interaction with the gas in the Galacticcenter can not only explain the measured high values of cosmic ray ionizationand heating rates but also contribute to nonthermal bremsstrahlung continuumemission, all of which are consistent with observations.

An OH(1720 MHz) Maser and a Nonthermal Radio Source in Sgr B2(M): A SNR--Molecular Cloud Interaction Site?