Uncovering a Massive z 7.7 Galaxy Hosting a Heavily Obscured Radio-loud Active Galactic Nucleus Candidate in COSMOS-Web

In this Letter, we report the discovery of the highest redshift, heavily obscured, radio-loud (RL) active galactic nucleus (AGN) candidate selected using JWST NIRCam/MIRI, mid-IR, submillimeter, and radio imaging in the COSMOS-Web field. Using multifrequency radio observations and mid-IR photometry, we identify a powerful, RL, growing supermassive black hole with significant spectral steepening of the radio spectral energy distribution (f (1.28 GHz) similar to 2 mJy, q (24 mu m) = -1.1, alpha (1.28-3) (GHz) = - 1.2, Delta alpha = - 0.4). In conjunction with ALMA, deep ground-based observations, ancillary space-based data, and the unprecedented resolution and sensitivity of JWST, we find no evidence of AGN contribution to the UV/optical/near-infrared (NIR) data and thus infer heavy amounts of obscuration (N- H > 10(23) cm(-2)). Using the wealth of deep UV to submillimeter photometric data, we report a singular solution photo-z of z (phot) = 7.7(-0.3)(+0.4) and estimate an extremely massive host galaxy (log M-star=11.92 +/- 0.5M(circle dot)) hosting a powerful, growing supermassive black hole (L (Bol) = 4-12x x 10(46) erg s(-1)). This source represents the farthest known obscured RL AGN candidate, and its level of obscuration aligns with the most representative but observationally scarce population of AGN at these epochs.